JPH0773791B2 - Narrow groove horizontal welding method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrow groove lateral welding method, and more particularly to a welding method which does not cause welding defects such as poor fusion and defective bead shape when welding in a horizontal posture.

(Prior Art) When welding in a horizontal position, there is a problem that the weld metal sags due to gravity. Generally, welding defects are more likely to occur than in the downward position, and it is difficult to achieve high efficiency. 1 more pass /
It becomes more difficult in narrow groove welding that performs layer welding.

FIG. 6 shows an outline of conventional narrow groove lateral welding. In FIG. 6, 1 is a base material steel plate and 2 is a weld metal. That is, in high-efficiency welding in which the heat input is increased and the amount of deposition per layer is large, the weld metal easily sags, and welding defects such as poor fusion and defective bead shape are likely to occur.

Therefore, as shown in FIG. 7 (A), a method of performing multi-layer welding with a small heat input and a small amount of welding, or as shown in FIG. 7 (B), the center of the groove is formed at an angle of θ with respect to the horizontal plane. Although a method of welding with a relatively high heat input is used, there are drawbacks that the welding efficiency is low in (A) and the groove work is difficult in (B) and the welding plate thickness becomes thick. In addition, 1 and 2 in FIG. 7 indicate the base material steel plate and the weld metal in the same manner as described in FIG.

(Problems to be Solved by the Invention) The present invention is intended to provide a welding method that can be performed with high efficiency without welding defects such as fusion defects and bead shape defects as in conventional narrow groove lateral welding. is there.

(Means for Solving Problems) The present inventors have proposed a method of stirring a molten metal by using magnetism. However, the present invention provides the molten metal stirring force of molten metal in narrow groove lateral welding. By using it as a lifting force to counteract gravity, it is possible to perform welding work with high quality even in highly efficient large heat input welding. That is, the present invention uses a low-frequency pulse current as the welding current, the excitation coil provided around the tungsten electrode or the welding wire, so that the weld metal solidification portion is lifted up at the peak of the low-frequency pulse current, Further, it is a narrow-open horizontal welding method characterized by welding while applying a magnetic field so that it can be lowered at the base.

INDUSTRIAL APPLICABILITY The present invention can be advantageously applied to the production of all products using welding in a horizontal orientation such as chemical machinery, nuclear equipment, pressure vessels such as tanks, ships, marine structures, and steel structures.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is an external view thereof, FIG. 2 is a principle view, and FIG. 3 is a view of FIG. 2 viewed from the right side.

1-3, 1 is a base material steel plate, 2 is a weld metal, 3
Is a weld metal, 4 is a tungsten electrode, 5 is a power supply chip,
6 is a shield nozzle, 7 is a low frequency pulse welding power source, 8 is an exciting coil, 9 is a magnetic conductor, 10 is an alternating magnetic field generating power source, 11 is a synchronizing cable, 12 is a welding current, 13 is a magnetic field, and 14 is an electromagnetic force (Lorentz). F), 15 is a welding wire, 16 is a wire heating current feeding chip, 17 is a wire heating power source, and 18 is a wire feeding roller.

When inserting the tungsten electrode 4 into the narrow groove and performing the horizontal hot spot TIG welding of the narrow groove, the exciting coil 8 provided around the tungsten electrode 4 is synchronized with the low frequency pulse of the welding current to generate a low frequency alternating current. And a mechanism for preventing the molten metal from dropping down by an electromagnetic force (Lorentz force) generated by the welding current and the magnetic field.

The present invention can be applied not only to TIG welding but also to MIG welding, submerged arc welding and the like.

(Operation) FIG. 4 is a view for explaining the operation of the present invention.

The welding current is a low frequency DC square wave. In horizontal welding, a frequency of 1-10Hz is used to prevent dripping. In synchronization with this, a low-frequency AC rectangular wave is supplied as an exciting current.

In this case, in A of the base current region, a force of clockwise rotation is generated in the molten metal to lower the molten metal. Next, in B of the peak current region, a counterclockwise rotation force is generated in the molten metal to try to lift the molten metal. Since IB> IA here, the force to raise the molten metal is generated as a whole.

Further, as shown in the form of the molten metal, in A, the molten pool 3 is small and does not easily drip, and in B, the molten pool 3 is large, but the molten pool 3 is held so as not to drip by the pulling force, and good horizontal welding is possible. Further, the magnetic stirring effect makes the bead shape flat and prevents defective fusion, and the stirring effect also makes it possible to prevent hot cracking and blowholes by refining the crystal grains. Therefore, high quality and high efficiency horizontal welding of narrow groove is possible.

Example A narrow groove was provided in 50 mm austenitic stainless steel as shown in FIG. 5, and the conventional method and the method of the present invention were applied under the conditions shown in the table below. The results are also shown in the table below.

As is clear from the above table, even with the conventional method, when the wire feeding speed is low (500 mm / min), no defects occur,
When the wire feeding speed is increased to increase the welding efficiency (1500 mm / min), the bead shape deteriorates, sagging occurs, and fusion failure occurs near the groove surface.

However, when the magnetic stirring is performed in synchronism with the pulse current as in the method of the present invention, the wire feeding speed is increased (1500 mm / mi
n), high quality welding with no fusion failure and no fusion failure can be performed with high efficiency.

Further, the stirring effect causes the crystal grains to become finer, the ultrasonic wave transmission performance is good, and the nondestructive inspection accuracy is improved. Furthermore, since high-temperature cracking is less likely to occur, the amount of δ-ferrite required for preventing high-temperature cracking can be reduced, so constant temperature toughness can be improved, σ-phase embrittlement can be prevented, and magnetic permeability can also be improved. Can be manufactured.

[Brief description of drawings]

1 to 3 are views for explaining an embodiment of the present invention, in which FIG. 1 is an external view thereof, FIG. 2 is a principle view, and FIG. 3 is a view of FIG. 2 viewed from the right side. Is. FIG. 4 is a diagram for explaining the operation of the present invention, and FIG. 5 is a diagram showing the narrow groove of austenitic stainless steel adopted in the examples of the present invention. FIG. 6 is a diagram for explaining a defect in narrow groove lateral welding in the conventional method, and FIG. 7 is a diagram showing a mode of narrow groove lateral welding in the conventional method.

Claims (1)

[Claims] 1. A low-frequency pulse current is used as a welding current, and an exciting coil provided around a tungsten electrode or a welding wire is provided so that a weld metal solidification portion is lifted up at the peak of the low-frequency pulse current. Also, a narrow groove lateral welding method characterized by welding while applying a magnetic field so that the base can be lowered.